They only have done it for cattle people and for a short while, for goats. Very few have sheep and TSC is cheaper, but a massive hassle to get them to do their jobs, so few bother with the mill. Few bother with trying to get sheep feed from TSC, too.Since the horse feed specifically warns not to feed to sheep, I would obey those warnings and stay away from it for sheep. The problem is probably the amount of copper contained in the feed. Like Bay asked, why do you want to use this feed for your sheep?
The protein percentage is only 12% which is fairly low. What is the reason you want to feed this horse feed to your sheep instead of a formulated sheep ration? Sheep rations are safe since they are formulated with the correct amounts of minerals needed for the ovine species. They are also formulated to provide the specific amount of protein and fat to the age group being fed.
If you want to formulate your own feed, you need to know what the protein and mineral count is in your hay or pasture currently being fed in order to have the correct mix of ingredients. Different types of hay has different protein counts. So does pasture, depending on whether it is green pasture or dry pasture. Then you need to know the protein level in the different grains you want to blend together in order to provide the desired protein levels. Finally, you need to know what the mineral count is in all those things to determine the correct amounts of minerals to add to the blend. Just putting together what you think might work could be dangerous to the sheep, either in overloading, not providing enough, or using the wrong ratios.
If you have access to a feed mill, check and see what they are bagging and selling for other sheep breeders/raisers. You might find that someone in your area has already done all that work for you and you can simply buy their mix. I know of 2 mills in California that were already doing just that for sheep producers in their area and you could buy that mix from the mill. It was not any more expensive than other brands of sheep feed.
Bay, lysine is a by product of grain fermentation....could be if you fermented your pig feed, you could not only save money on feed by almost half, but also get the lysine they need. Would also keep them healthier while making the meat taste better. One lady ferments her feed in a big plastic trash can and dishes it out by the shovel full.I feed my horses, sheep, and pigs an all purpose pellet. It does not have lysine in it, an essential pig nutrient, so I give them boiled eggs.